1# strstr.m4 serial 17
2dnl Copyright (C) 2008-2017 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7dnl Check that strstr works.
8AC_DEFUN([gl_FUNC_STRSTR_SIMPLE],
9[
10  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
11  AC_REQUIRE([gl_FUNC_MEMCHR])
12  if test "$gl_cv_func_memchr_works" != yes; then
13    REPLACE_STRSTR=1
14  else
15    dnl Detect http://sourceware.org/bugzilla/show_bug.cgi?id=12092.
16    AC_CACHE_CHECK([whether strstr works],
17      [gl_cv_func_strstr_works_always],
18      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
19#include <string.h> /* for strstr */
20#define P "_EF_BF_BD"
21#define HAYSTACK "F_BD_CE_BD" P P P P "_C3_88_20" P P P "_C3_A7_20" P
22#define NEEDLE P P P P P
23]], [[return !!strstr (HAYSTACK, NEEDLE);
24    ]])],
25        [gl_cv_func_strstr_works_always=yes],
26        [gl_cv_func_strstr_works_always=no],
27        [dnl glibc 2.12 and cygwin 1.7.7 have a known bug.  uClibc is not
28         dnl affected, since it uses different source code for strstr than
29         dnl glibc.
30         dnl Assume that it works on all other platforms, even if it is not
31         dnl linear.
32         AC_EGREP_CPP([Lucky user],
33           [
34#ifdef __GNU_LIBRARY__
35 #include <features.h>
36 #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ > 12) || (__GLIBC__ > 2)) \
37     || defined __UCLIBC__
38  Lucky user
39 #endif
40#elif defined __CYGWIN__
41 #include <cygwin/version.h>
42 #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7)
43  Lucky user
44 #endif
45#else
46  Lucky user
47#endif
48           ],
49           [gl_cv_func_strstr_works_always="guessing yes"],
50           [gl_cv_func_strstr_works_always="guessing no"])
51        ])
52      ])
53    case "$gl_cv_func_strstr_works_always" in
54      *yes) ;;
55      *)
56        REPLACE_STRSTR=1
57        ;;
58    esac
59  fi
60]) # gl_FUNC_STRSTR_SIMPLE
61
62dnl Additionally, check that strstr is efficient.
63AC_DEFUN([gl_FUNC_STRSTR],
64[
65  AC_REQUIRE([gl_FUNC_STRSTR_SIMPLE])
66  if test $REPLACE_STRSTR = 0; then
67    AC_CACHE_CHECK([whether strstr works in linear time],
68      [gl_cv_func_strstr_linear],
69      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
70#ifdef __MVS__
71/* z/OS does not deliver signals while strstr() is running (thanks to
72   restrictions on its LE runtime), which prevents us from limiting the
73   running time of this test.  */
74# error "This test does not work properly on z/OS"
75#endif
76#include <signal.h> /* for signal */
77#include <string.h> /* for strstr */
78#include <stdlib.h> /* for malloc */
79#include <unistd.h> /* for alarm */
80static void quit (int sig) { _exit (sig + 128); }
81]], [[
82    int result = 0;
83    size_t m = 1000000;
84    char *haystack = (char *) malloc (2 * m + 2);
85    char *needle = (char *) malloc (m + 2);
86    /* Failure to compile this test due to missing alarm is okay,
87       since all such platforms (mingw) also have quadratic strstr.  */
88    signal (SIGALRM, quit);
89    alarm (5);
90    /* Check for quadratic performance.  */
91    if (haystack && needle)
92      {
93        memset (haystack, 'A', 2 * m);
94        haystack[2 * m] = 'B';
95        haystack[2 * m + 1] = 0;
96        memset (needle, 'A', m);
97        needle[m] = 'B';
98        needle[m + 1] = 0;
99        if (!strstr (haystack, needle))
100          result |= 1;
101      }
102    return result;
103    ]])],
104        [gl_cv_func_strstr_linear=yes], [gl_cv_func_strstr_linear=no],
105        [dnl Only glibc > 2.12 on processors without SSE 4.2 instructions and
106         dnl cygwin > 1.7.7 are known to have a bug-free strstr that works in
107         dnl linear time.
108         AC_EGREP_CPP([Lucky user],
109           [
110#include <features.h>
111#ifdef __GNU_LIBRARY__
112 #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ > 12) || (__GLIBC__ > 2)) \
113     && !(defined __i386__ || defined __x86_64__) \
114     && !defined __UCLIBC__
115  Lucky user
116 #endif
117#endif
118#ifdef __CYGWIN__
119 #include <cygwin/version.h>
120 #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7)
121  Lucky user
122 #endif
123#endif
124           ],
125           [gl_cv_func_strstr_linear="guessing yes"],
126           [gl_cv_func_strstr_linear="guessing no"])
127        ])
128      ])
129    case "$gl_cv_func_strstr_linear" in
130      *yes) ;;
131      *)
132        REPLACE_STRSTR=1
133        ;;
134    esac
135  fi
136]) # gl_FUNC_STRSTR
137